Probing Downstream Olive Biophenol Secoiridoids.

Ganapathy Sivakumar,Nicola Uccella,Luigi Gentile

doi:10.3390/ijms19102892

Abstract

Numerous bioactive biophenol secoiridoids (BPsecos) are found in the fruit, leaves, and oil of olives. These BPsecos play important roles in both the taste of food and human health. The main BPseco bioactive from green olive fruits, leaves, and table olives is oleuropein, while olive oil is rich in oleuropein downstream pathway molecules. The aim of this study was to probe olive BPseco downstream molecular pathways that are alike in biological and olive processing systems at different pHs and reaction times. The downstream molecular pathway were analyzed by high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI/MS) and typed neglected of different overlap (TNDO) computational methods. Our study showed oleuropein highest occupied molecular orbital (HOMO) and HOMO-1 triggered the free radical processes, while HOMO-2 and lowest unoccupied molecular orbital (LUMO) were polar reactions of glucoside and ester groups. Olive BPsecos were found to be stable under acid and base catalylic experiments. Oleuropein aglycone opened to diales and rearranged to hydroxytyrosil-elenolate under strong reaction conditions. The results suggest that competition among olive BPseco HOMOs could induce glucoside hydrolysis during olive milling due to native olive β-glucosidases. The underlined olive BPsecos downstream molecular mechanism herein could provide new insights into the olive milling process to improve BPseco bioactives in olive oil and table olives, which would enhance both the functional food and the nutraceuticals that are produced from olives.

Highlights

Olive oil and table olives are a major part of the traditional food in the Mediterranean Aliment Culture (MAC) [1]
We found that olive biophenol secoiridoids (BPsecos) were stable under base catalysis and were hydrolyzed under acid and enzyme catalysis
The oleuropein frontier molecular orbital (FMO) results suggested that downstream pathways competed with free radical and polar molecular dynamics resulting from HO-aromatics and secoiridoid moieties, respectively

Summary

Introduction

Olive oil and table olives are a major part of the traditional food in the Mediterranean Aliment Culture (MAC) [1]. Extra virgin olive oil is one of the essential sources of monoenoic fatty acids and biophenol (BP)-based bioactives [10,11]. The major BPs from olive products include phenolic acids and alcohols as well as secoiridoids, while the minor contents are flavonoids and lignans [12]. The primary olive fruit biophenol secoiridoids (BPsecos) are oleuropein, ligstroside, and their demethylhomologues, which may have potential anticancer effects [13,14]. Olive leaves contain a higher concentration of BPs with secos of 1450 mg/100 FW (fresh weight) compared to the olive fruit and oil, which have 110 mg/100 g and 23 mg/100 mL, respectively [9].

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Conclusion